# How do you simplify sqrt(81x^4)?

$9 {x}^{2}$
You can calculate the root separately for $81$ and for ${x}^{4}$:
$\sqrt{81 {x}^{4}} = \sqrt{81 \cdot {x}^{4}} = \sqrt{81} \cdot \sqrt{{x}^{4}} = 9 {x}^{2}$.